The permeabilities and transport mechanisms of H+/OH- and acids and bases will be studied in planar lipid bilayer membranes of differing phospholipid, cholesterol and solvent composition. Permeabilities will be measured by a combination of radiotracer, PH electrode and electrical techniques. Initially we will determine membrane permeabilities and transport mechanisms for protons and hydrochloric acid. Our objective is to explain why the reported permeabilities of lipid bilayers to N+/OH- and CH- are orders of magnitude higher than the permeabilities to Na+ and K+. We will also study transport of fluoride and hydrofluoric acid in order to test the hypothesis that F- transport through biological membranes is attributable to nonionic diffusion of HF. We will then measure permeabilities to various organic acids and bases, beginning with monocarboxylic fatty acids. Our objectives are to resolve an important controversy about the methodology of measuring acid/base permeability and to explain a number of anomolous observations on organic acid transport in the intestine. The achievement of these objectives requires an analysis of the effects of chemical reactions in the aqueous unstirred layers. Finally, we will measure hydrocarbon/water partition coefficients and solute diffusion coefficients in hydrocarbons of varying chain length and viscosity. Our objective is to examine the relation between permeability, lipid solubility and diffusion coefficients for a variety of very small, but chemically differing solutes, e.g., H2O, HCl, HF, HNO3, HCOOH, NH3, etc. Our hypothesis is that the selectivity to water and very small solutes observed in biological and lipid bilayer membranes can be explained by a simple solubility-diffusion model, provided that the "viscosity independent" diffusion of very small molecules in hydrocarbon solvents is taken into account.